First amp build completed

There's something not right if a 5F6A's breakup is terrible.

See this if you're interested in adding a bias circuit by tapping the high voltage:

https://robrobinette.com/Generic_Tube_Amp_Mods.htm#High_Voltage_Tap_Adjustable_Bias

 

I think you have to use something like SoundCloud, and link to it. Easiest to record a phone video and put it in YouTube and link to it. Or if you make a nice audio recording, use SoundCloud.

 

The lead dress could be suspect. Parasitic oscillations can cause some of the troubles you’re experiencing.

 

I don’t have time to sort out your layout, brother. Once I’m back in my home state I can look.

 

Sounds like 120Hz hum and might be caused by bad grounding or problems with the filtering of the power supply. Your ground scheme is a bit unclear from the picture.
You could try to pull one tube at a time starting from V1 and see if you can locate the problem that way.
But if the hum is unaffected by the master volume, the problem probably lies in the PI or output stage or comes from the power supply.

 

Another way, if you have an audio-video editing program (the most basic freeware will suffice), is record the sound of the amp and pair it with a still photo of the amp, then upload to YouTube.

 

Hey, glad you worked it out. That wiring style always impresses me. There’s something so raw, chest hairy, and organic about it. I can literally imagine the odor of it; like an old rusty battleship. And Lol @ your “surprised it worked” comment! I switched on my first build with a broomstick handle from behind a chair!

If you want the sweetest and juiciest fender tone around, try to match the the plates to the AA964. But! If you still insist on having the lowly Bassman sound (jk!), there are some areas to play with.

Investigate your voltages throughout. If your pt is supplying on spec for that 5f6a circuit and you still find it too stiff, you can loosen it up a bit by lowering first stage filtering a smidge, playing with preamp voltages, or getting yourself a lively, medium efficiency speaker.

Yes, this least sexy option, and the one that doesn’t let you play with your soldering iron or enjoy the rich aroma of solder, can be the ticket to tuna town for you. After 20 years of building and modding, I’ve literally just stumbled across the importance of speaker selection for acquiring vintage fender tone. I’m a dense man at times and have seen this advice for decades.

For context, I played lead guitar in a touring modern rock band and relied on overly efficient drivers with massive power handling to give me tight and saturated tones. My love of Phrygian shreddy things yielded to more organic blues-based noodley-feels and I decided to have a gear makeover. Out went the coliseum head and in came the blackface clone builds. No, I’ve never played a coliseum.

Guess what can happen when you use speakers like these with vintage circuits? You can get stiff and lifeless tone - with no lively interaction and feel beneath the fingers. This sent me spinning off in the wrong direction for years.

I took a chance on a Vibrolux clone a few months ago, but it came with a pair of high efficiency drivers. I was so disappointed with the stifff and lifeless feel. Very strident, as well. Then after more research, the advice I ignored or denied bubbled up. I took a gamble on a pair of low wattage/efficiency Webers and the cloud and haze of my own, decades old dumbassery lifted and lights from the heavens shone down. Angels wept. There it was. The tone and feel I always wanted and the actual feeling that the speakers were wired right to my fingertips. Transformative.

Anyway I’m blabbering on. No sleep the last week. Congrats and huge props for diggging your heels in and doing the work. I’ve fallen victim to my own sloth many times, as I waited for answers to arrive instead of doing the work and actually learning.

 

I didn't know you felt that way about me... lol

Sent from my KIW-L24 using Tapatalk

 

I just can’t quit you

It’s funny how hypersensitive you can become when fooling around with lethal voltages lol. Messing with a reverb amp is like that, too. The slightest bump and you get that massive spring explosion sound.

So, your clean tone is glorious. How do you feel about the character of the crunch tone aside from the stiffness? Is there any transition at all into overdrive?

Reason I ask is because sometimes the change a different speaker brings is more related to a shift in the onset of overdrive relative to volume. Sooner or later breakup. Sometimes it’s the quality of the breakup itself. Jagged edges vs smooth mids.

The bassman should have sone nice compression as it starts transitioning into od and that, coupled with the compression from the speakers (if it exists in your scenario), should give you the squish you are looking for.

This is all speculation; your voltage measurements will speak volumes (honk honk!) about what’s going on. If you have time to compare against the original schematic and share, that would be helpful to those looking to help you adjust your tone. Bias, plate, screen, etc.

Wait a minute - what’s the spec on your output transformer? Any idea what that old Bogen was putting out? I once built an ab763 clone using a spare 100w ot I had lying around. Clean was amazing, but thing was super stiff and the overdrive was very flat and dimensionless. I tweaked and tweaked the filtering and plate voltages for months. Then I stripped it down, modding the power amp to run at 35w with two tubes and smaller ot. Bingo!

It was at that moment I realized the magic juju for me lied within the smaller ot (and lower plate voltages would be the second thing I’d come to discover much later on the journey).

 

Get those volts squared away! You may be in love after that. Then I’d look at the ot.

Cheers!

 

How is the over all volume?


Does it get as loud as you think it should?

 

+1 on the OT suggestion; ditto on the speaker significance. Both can be transformative.